This invention relates to a magnetic head, a recording and/or playback method for a tape-type magnetic recording medium and a rotary magnetic head mechanism.
Various apparatus for recording and playing back a signal onto and from a tape-type magnetic recording medium are known and widely used. An exemplary one of apparatus of the type mentioned is a video cassette recorder apparatus of a rotary drum type wherein a magnetic head mounted on a rotating drum forms and records a track having an inclination angle on a tape-type magnetic recording medium and further traces and plays back the inclined track. Particularly recently, a video tape recorder (VTR) apparatus compliant with digital standards has been popularized.
One of tape-type magnetic recording media is a coat-type magnetic tape. The coat-type magnetic tape has a structure wherein a magnetic layer or a magnetic face is formed on a plastic base material by applying acicular or particulate magnetic powder to the plastic base material using a binder as an adhesive. The magnetic face of the coat-type magnetic tape has a coercive force Hc and a residual magnetic flux density Br which are inclined to increase as the recording density increases. For example, with an MP tape compliant with the DV standards, the coercive force Hc reaches 2,300 oersted and the residual magnetic flux density reaches 3,000 gauss.
On the other hand, the size of the simple substance of the magnetic powder decreases to 0.1xc3x971.0 xcexcm with a coat-type metal tape. Further, as regards the tape thickness, while tapes of approximately 10 to 16 xcexcm thick are conventionally used on editing machines, the tape thickness is decreased in order to satisfy the demand for miniaturization of a tape cassette and for recording and playback for a long period of time. Now, the tape thickness of a tape-type magnetic recording medium for a digital video signal compliant with the DV standards is 7 to 8 xcexcm.
Therefore, it is necessary for an apparatus for recording/playing back onto/from a magnetic tape of such a characteristic as just described to be contrived in terms of a fluidic interference function relating to control of physical contact with the magnetic tape and a magnetic interference function relating to recording/playback.
An exemplary one of magnetic tape recording/playback apparatus of the type described is a rotary magnetic head mechanism which records/plays back onto/from a magnetic tape medium while rotating. A conventional rotary magnetic head mechanism of the type just mentioned adopts a magnetic head which operates in accordance with the principle of magnetic induction. In the magnetic head, magnetic poles are opposed to each other with a very small head gap left therebetween, and a magnetic face of a magnetic tape medium is disposed perpendicularly to and very close to the head gap. Upon recording, magnetic lines of force generated from the magnetic poles when they are driven magnetize a magnetic substance which forms the magnetic face of the magnetic tape medium while the magnetic lines of force pass from one to the other of the magnetic poles through the head gap and the magnetic face to record on the magnetic tape medium. On the other hand, upon playback, leakage fluxes generated from the magnetic substance which forms the magnetic face of the magnetic tape medium are caught through the head gap by the magnetic poles to detect an electromotive force generated by electromagnetic induction when the leakage fluxes vary as the magnetic tape medium is fed.
In order to raise the recording density and assure a high S/N (signal to noise) ratio, it is necessary for the magnetic tape medium to closely contact with the head gap and besides it is necessary to maintain stable movement of the tape while such close contact of the tape is maintained.
Conventionally, in order to realize the close contacting state described above, the magnetic tape medium is pressed against the head gap to obtain a necessary contact pressure. Particularly with a rotary magnetic head mechanism, the contact pressure is obtained by a tension applied to the magnetic tape medium. FIGS. 11 to 13 show a configuration of a conventional rotary magnetic head mechanism of the type described.
Referring to FIGS. 11 to 13, a rotary magnetic head mechanism 100 shown includes a cylindrical rotary drum 101 having a head window 102 formed in a recessed relationship therein such that it is open on a part of circumferential face of the cylindrical rotary drum 101, and a magnetic head 104 having a head gap 103 and disposed in the head window 102. The rotary magnetic head mechanism 100 is rotated at a predetermined speed in a rotational direction 106. Upon rotation of the rotary magnetic head mechanism 100, also the magnetic head 104 moves at an equal speed. Tension 107 is applied to a magnetic tape medium 105 which extends along the rotary drum 101 such that the magnetic tape medium 105 is pressed against the head gap 103 by the tension 107 and therefore is fed in the same direction at a speed lower than that of the magnetic head 104. A cylindrical fixed drum 111 is disposed in a little spaced relationship below the rotary drum 101.
In order to assure a good contact state between the head gap 103 and the magnetic tape medium 105, a face 108 of the rotary magnetic head mechanism 100 around the head gap 103 along which the rotary magnetic head mechanism 100 contacts with the magnetic tape medium 105 is formed as a curved face of a curvature 109 which is convex in a recording track direction, that is, a magnetic tape feeding direction and is formed also as a curved face of a curvature 110 which is convex also in a track width direction and besides the face 108 projects from the cylindrical face of the rotary drum 101 together with the head gap 103.
When the magnetic tape medium 105 contacts with the magnetic head 104 having the configuration just described with a pressing force caused by the tension 107, the magnetic tape medium 105 is deformed into a convex shape along the face 108 of the magnetic head 104 and a good contact state between the magnetic head 104 and the magnetic tape medium 105 can be assured. Meanwhile, a portion of the magnetic tape medium 105 which does not contact with the magnetic head 104 is sometimes deformed by the gaps between the head window 102 and the rotary drum 101 and fixed drum 111.
As described above, the rotary magnetic head mechanism 100 of the conventional configuration applies sufficient tension 107 to the magnetic tape medium 105 to compulsorily press the magnetic tape medium 105 against the magnetic head 104 of a convex shape to assure a good contact state between them thereby to make use of magnetic interference between the magnetic head 104 and the magnetic tape medium 105 to effect magnetic recording or playback of the magnetic tape medium 105.
The rotary magnetic head mechanism 100, however, has a problem that, since the magnetic tape medium 105 is compulsorily pressed against the magnetic head 104 of a convex shape as described above, the head gap 103 is liable to be abraded by the magnetic tape medium 105, resulting in reduction of the life of the head gap 103. Simultaneously, there is another problem that the magnetic face of the magnetic tape medium 105 is liable to be abraded similarly and suffer from irreversible deformation, resulting in reduction of the life of the magnetic tape medium 105.
Therefore, in order to assure a long life of the head, the rotary magnetic head mechanism 100 is conventionally designed such that the depthwise dimension of the head gap 103, that is, the gap depth, is set so deep as to have a suitable margin. In particular, for example, the gap depth is initially set as deep as 20 to 30 xcexcm to assure a long interval of time until the gap depth is decreased to its limit value by abrasion of the magnetic head 104 thereby to assure a long life of the rotary magnetic head mechanism 100.
However, the countermeasure that the initial gap depth is set deep as described above is disadvantageous in that there is a limit to improvement in sensitivity and high density recording cannot be anticipated while there is a limitation to high density playback. Further, the countermeasure is not effective to eliminate the disadvantage of the reduction of the life of the tape described above.
Furthermore, the countermeasure does not provide measures for applying, to a tape-type magnetic recording medium, an MR head or a GMR head of the magneto-resistance effect type (or the magnetic flux response type) which is applied principally to magnetic hard disk apparatus (HDD: hard disk drive) and makes use of a magneto-resistance effect to detect a magnetic field variation on a recording medium with a very shallow gap depth.
It is an object of the present invention to provide a magnetic head, a recording and/or playback method for a tape-type magnetic recording medium and a rotary magnetic head mechanism by which a good contact state between the head and a tap medium can be assured with a decreased contact pressure to reduce the abrasion of the head and the tape medium to assure a long life for the head and the tape.
It is another object of the present invention to provide a magnetic head, a recording and/or playback method for a tape-type magnetic recording medium and a rotary magnetic head mechanism by which a head of the magneto-resistance effect type can be applied to a tape medium.
In order to attain the objects described above, according to an aspect of the present invention, there is provided a magnetic head mounted on a rotary drum having an outer circumferential face along which a tape-type magnetic recording medium can be wrapped such that the magnetic head moves by rotation of the rotary drum and contacts with the tape-type magnetic recording medium to record or play back the tape-type magnetic recording medium, having a face portion opposing to the tape-type magnetic recording medium when the magnetic head moves, and a recording and/or playback element for contacting with the tape-type magnetic recording medium to perform at least one of magnetic recording and playback of the tape-type magnetic recording medium, the face portion being a smooth flat face which extends perpendicularly to a diametrical direction of the rotary drum and is positioned on the inner circumferential side retracted from the outer circumferential face of the rotary drum, the recording and/or playback element being disposed within a range of the face portion within which the tape-type magnetic recording medium contacts.
In the magnetic head, the face portion formed from a smooth flat face for fluidically interfering with a tape-type magnetic recording medium extends perpendicularly to a diametrical direction of the rotary drum and is positioned on the inner circumferential side retracted from the outer circumferential face of the rotary drum so as to form a recessed portion such that the tape-type magnetic recording medium is contacted with the face portion, and the recording and/or playback element for magnetically interfering with the tape-type magnetic recording medium is disposed within a range of the face portion within which the tape-type magnetic recording medium contacts. When the drum rotates, the pressure within the recessed portion formed by the smooth flat face is decreased, and consequently, the tape-type magnetic recording medium is attracted toward the smooth flat face of the rotary drum. Since the magnetic head includes the smooth flat face extending perpendicularly to a diametrical direction of the rotary drum, when the rotary drum rotates, the smooth flat face advances in a tangential direction to the rotary drum, whereupon an air flow is formed in the tangential direction on the smooth flat face. Meanwhile, the tape-type magnetic recording medium approaches the smooth flat face by the attraction as described above. As a result, pressure reduction in accordance with the Bernoulli""s theorem occurs with the air flow which flows in a narrow path defined by the tape-type magnetic recording medium and the smooth flat face, and due to the pressure reduction effect, the tape-type magnetic recording medium gradually approaches and contacts with the smooth flat face. Consequently, the tape-type magnetic recording medium contacts with a contact pressure with the recording and/or playback element without applying compulsory force to the tape-type magnetic recording medium. In this manner, the tape-type magnetic recording medium having approached the smooth flat face by the attracting action of the recessed portion can be contacted with the smooth flat face with a suitable contact pressure only by the pressure reduction effect of the air flow generated naturally by the advancement of the smooth flat face. Consequently, recording or playback can be performed while suppressing abrasion of the tape-type magnetic recording medium and the magnetic head.
According to another aspect of the present invention, there is provided a magnetic head mounted on a rotary drum having an outer circumferential face along which a tape-type magnetic recording medium can be wrapped such that the magnetic head is smaller in size than and is disposed in an exposed state in a window portion formed in a concave state on the outer circumferential face of the rotary drum with a pair of air gaps formed between the magnetic head and the opposite ends of the window portion and that the magnetic head moves by rotation of the rotary drum and contacts with the tape-type magnetic recording medium to record or play hack the tape-type magnetic recording medium, having a face portion opposing to the tape-type magnetic recording medium when the magnetic head moves, and a recording and/or playback element for contacting with the tape-type magnetic recording medium to perform at least one of magnetic recording and playback of the tape-type magnetic recording medium, the face portion being a smooth flat face which extends perpendicularly to a diametrical direction of the rotary drum and is positioned on the inner circumferential side retracted from the outer circumferential face of the rotary drum, the recording and/or playback element being disposed within a range of the face portion within which the tape-type magnetic recording medium contacts.
In the magnetic head, the face portion having a size smaller than a window portion formed in a concave state on the outer circumferential face of the rotary drum for fluidically interfering with a tape-type magnetic recording medium is disposed as a smooth flat face which extends perpendicularly to a diametrical direction of the rotary drum and is positioned on the inner circumferential side retracted from the outer circumferential face of the rotary drum so as to form a pair of air gaps between the opposite ends of the window portion and the opposite ends of the face portion, and the recording and/or playback element for magnetically interfering with the tape-type magnetic recording medium is disposed within a range of the face portion within which the tape-type magnetic recording medium contacts. When the drum rotates, the pressures within the air gaps formed between the opposite ends of the magnetic head and the opposite ends of the window portion are reduced, and consequently, the tape-type magnetic recording medium is effectively attracted toward the smooth flat face of the rotary drum.
Meanwhile, since the magnetic head configured as described above includes the smooth flat face extending perpendicularly to a diametrical direction of the rotary drum and positioned on the inner circumferential side retracted from the outer circumferential face of the rotary drum, when the rotary drum rotates, the smooth flat face advances in a tangential direction to the rotary drum, whereupon an air flow is formed in the tangential direction on the smooth flat face. Meanwhile, the tape-type magnetic recording medium approaches the smooth flat face positioned on the inner circumferential side retracted from the outer circumferential face of the rotary drum by the attraction as described above. As a result, the air flow which flows in the tangential direction on the smooth flat face flows along a narrow path defined by the tape-type magnetic recording medium and the smooth flat face, and consequently, pressure reduction in accordance with the Bernoulli""s theorem occurs with the air flow. Thus, due to the pressure reduction effect, the tape-type magnetic recording medium gradually approaches and contacts with the smooth flat face. Consequently, the tape-type magnetic recording medium contacts with a contact pressure with the recording and/or playback element without applying compulsory force to the tape-type magnetic recording medium. In this manner, the tape-type magnetic recording medium having approached the smooth flat face by the attracting action of the recessed portion can be contacted with the smooth flat face with a suitable contact pressure only by the pressure reduction effect of the air flow generated naturally by the advancement of the smooth flat face. Consequently, recording or playback can be performed while suppressing abrasion of the tape-type magnetic recording medium and the magnetic head.
In either of the magnetic heads, the face portion may be formed from a smooth curved face having a curvature more moderate than that of the rotary drum and having a tangential direction at least at one position on the smooth curved face which extends perpendicularly to a diametrical direction of the rotary drum.
The state of the air flow which provides the pressure reduction effect relies upon the shape and the smoothness of the face portion, and where the smoothness is the same, the pressure reduction effect by an air flow generated by a smooth curved face of a moderate curvature is higher than the pressure reduction effect by an air flow generated by a smooth curved face of a greater curvature. In the magnetic head, since the face portion is formed from a smooth curved face having a curvature more moderate than that of the rotary drum and having a tangential direction at least at one position on the smooth curved face which extends perpendicularly to a diametrical direction of the rotary drum, an air flow is formed in the same direction as the advancing direction of the magnetic head on the smooth flat face. Consequently, by a pressure reduction effect in accordance with the Bernoulli""s theorem caused by the air flow between the tape-type magnetic recording medium and the smooth curved face of a moderate curvature of the magnetic head, the approaching tape-type magnetic recording medium can be contacted with the smooth curved face and consequently with the recording and/or playback element.
According to a further aspect of the present invention, there is provided a recording and/or playback method for a tape-type magnetic recording medium, comprising the steps of wrapping the tape-type magnetic recording medium around a cylindrical rotary drum including a magnetic head which has a smooth flat face extending perpendicularly to a diametrical direction of the rotary drum or a smoothed curved face having a curvature more moderate than that of the rotary drum and having a tangential direction at least at one position thereof which extends perpendicularly to a diametrical direction of the rotary drum, the magnetic head being disposed such that the smooth flat face or smooth curved face is exposed at a position on the inner circumferential side retracted from an outer circumferential face of the rotary drum, the smooth flat face or smooth curved face having a recording and/or playback element disposed thereon for magnetically interfering with the tape-type magnetic recording medium, and causing the tape-type magnetic recording medium to contact with the recording and/or playback element by pressure reduction caused by fluidic interference between the smooth flat face or smooth curved face and the tape-type magnetic recording medium to execute at least one of recording and playback of the tape-type magnetic recording medium.
In the recording and/or playback method, the smooth flat face or smoothed curved face having a moderate curvature is positioned on the inner circumferential side retracted from the outer circumferential face of the rotary drum so as to form a recessed portion. When the drum rotates, the pressure within the recessed portion is reduced, and consequently, the tape-type magnetic recording medium is attracted toward the smooth flat face or smooth curved face of the rotary drum.
Since the smooth flat face extends perpendicularly to a diametrical direction of the rotary drum or the smoothed curved face has a tangential direction at least at one position thereof which extends perpendicularly to a diametrical direction of the rotary drum, when the rotary drum rotates, the smooth flat face or smooth curved face advances in a direction perpendicular to a diametrical direction of the rotary drum, whereupon an air flow is formed in the advancing direction on the smooth flat face or smooth curved face.
When the tape-type magnetic recording medium approaches the smooth flat face by the attraction described above, the air flow flows along a narrow path defined by the tape-type magnetic recording medium and the smooth flat face or by the tape-type magnetic recording medium and the smooth curved face. As a result, pressure reduction in accordance with the Bernoulli""s theorem occurs with the air flow, and due to the pressure reduction effect, the tape-type magnetic recording medium gradually approaches and contacts with the smooth flat face or smooth curved face. Consequently, the tape-type magnetic recording medium contacts with a contact pressure with the recording and/or playback element without applying compulsory force to the tape-type magnetic recording medium. In this manner, the tape-type magnetic recording medium can be contacted with the smooth flat face with a suitable contact pressure only by the pressure reduction effect of the air flow generated naturally by the advancement of the smooth flat face or smooth curved face. Consequently, recording or playback can be performed while suppressing abrasion of the tape-type magnetic recording medium and the magnetic head.
According to a still further aspect of the present invention, there is provided a recording and/or playback method for a tape-type magnetic recording medium, comprising the steps of wrapping the tape-type magnetic recording medium around a rotary drum having an outer circumferential face along which a tape-type magnetic recording medium can be wrapped and having a window portion formed in a concave state on the outer circumferential face thereof, the rotary drum including a magnetic head which has a smooth flat face of a size smaller than the window portion or a smoothed curved face having a curvature more moderate than that of the rotary drum, the rotary drum being disposed in the window portion such that the smooth flat face or smooth curved face is exposed at a position on the inner circumferential side retracted from an outer circumferential face of the rotary drum with a pair of air gaps formed between the magnetic head and the opposite ends of the window portion, the smooth flat face extending perpendicularly to a diametrical direction of the rotary drum or the smooth curved face having a tangential direction at least at one position thereof which extends perpendicularly to a diametrical direction of the rotary drum, the smooth flat face or smooth curved face having a recording and/or playback element disposed thereon for magnetically interfering with the tape-type magnetic recording medium, and causing the tape-type magnetic recording medium to contact with the recording and/or playback element by pressure reduction caused by fluidic interference between the smooth flat face or smooth curved face and the tape-type magnetic recording medium to execute at least one of recording and playback of the tape-type magnetic recording medium.
In the recording and/or playback method, when the rotary drum rotates, the pressures within the air gaps formed between the opposite ends of the smooth flat face or smooth curved face and the opposite ends of the window portion are reduced. Consequently, the tape-type magnetic recording medium is effectively attracted toward the smooth flat face or smooth curved face of the rotary drum.
Since the smooth flat face extends perpendicularly to a diametrical direction of the rotary drum or the smoothed curved face has a tangential direction at least at one position thereof which extends perpendicularly to a diametrical direction of the rotary drum, when the rotary drum rotates, the smooth flat face or smooth curved face advances in a direction perpendicular to a diametrical direction of the rotary drum, whereupon an air flow is formed in the advancing direction on the smooth flat face or smooth curved face.
When the tape-type magnetic recording medium approaches the smooth flat face or smooth curved face, which is positioned on the inner circumferential side retracted from the outer circumferential face of the rotary drum, by the attraction described above, the air flow flows along a narrow path defined by the tape-type magnetic recording medium and the smooth flat face or by the tape-type magnetic recording medium and the smooth curved face. As a result, pressure reduction in accordance with the Bernoulli""s theorem occurs with the air flow, and due to the pressure reduction effect, the tape-type magnetic recording medium gradually approaches and contacts with the smooth flat face or smooth curved face. Consequently, the tape-type magnetic recording medium contacts with a contact pressure with the recording and/or playback element without applying compulsory force to the tape-type magnetic recording medium. In this manner, the tape-type magnetic recording medium can be contacted with the smooth flat face with a suitable contact pressure only by the pressure reduction effect of the air flow generated naturally by the advancement of the smooth flat face or smooth curved face. Consequently, recording or playback can be performed while suppressing abrasion of the tape-type magnetic recording medium and the magnetic head.
According to a yet further aspect of the present invention, there is provided a rotary magnetic head mechanism, comprising a rotary drum mounted for rotation and having an outer circumferential face along which a tape-type magnetic recording medium can be wrapped, and a magnetic head mounted on the rotary drum and having a face portion movable by rotation of the rotary drum and opposing to the tape-type magnetic recording medium to fluidically interfere with the tape-type magnetic recording medium and a recording and/or playback element for contacting and magnetically interfering with the tape-type magnetic recording medium to execute at least one of recording and playback of the tape-type magnetic recording medium, the face portion being a smooth flat face which extends perpendicularly to a diametrical direction of the rotary drum and is positioned on the inner circumferential side retracted from the outer circumferential face of the rotary drum, the recording and/or playback element being disposed within a range of the face portion within which the tape-type magnetic recording medium contacts the face portion with fluidic interference.
In the rotary magnetic head mechanism, the face portion formed from a smooth flat face for fluidically interfering with a tape-type magnetic recording medium extends perpendicularly to a diametrical direction of the rotary drum and is positioned on the inner circumferential side retracted from the outer circumferential face of the rotary drum so as to form a recessed portion and the recording and/or playback element for magnetically interfering with the tape-type magnetic recording medium is disposed within a range of the face portion within which the tape-type magnetic recording medium contacts. When the drum rotates, the pressure within the recessed portion decreased, and consequently, the tape-type magnetic recording medium is attracted toward the smooth flat face of the rotary drum. This is a first stage.
Meanwhile, since the smooth flat face of the magnetic head extends perpendicularly to a diametrical direction of he rotary drum, when the rotary drum rotates, the smooth flat face advances in a tangential direction thereto, whereupon an air flow is formed in the tangential direction on the smooth flat face. The air flow flows along a narrow path defined by the smooth flat face and the tape-type magnetic recording medium having approached the smooth flat face at the retracted position by the attraction described above. As a result, pressure reduction in accordance with the Bernoulli""s theorem occurs with the air flow. Due to the pressure reduction effect, the tape-type magnetic recording medium gradually approaches and contacts with the smooth flat face. Consequently, the tape-type magnetic recording medium contacts with a contact pressure with the recording and/or playback element. This is a second stage
In this manner, thanks to a synergetic effect of the first and second stages provided only by rotation of the rotary drum, the tape-type magnetic recording medium can be contacted with the recording and/or playback element with a suitable contact pressure only by an effect of the air flow generated naturally without the necessity for applying compulsory force. Consequently, recording or playback can be performed while suppressing abrasion of the tape-type magnetic recording medium and the magnetic head.
According to a yet further aspect of the present invention, there is provided a rotary magnetic head mechanism, comprising a cylindrical rotary drum having an outer circumferential face along which a tape-type magnetic recording medium can be wrapped and which rotates at a predetermined linear velocity in a tangential direction and a window portion formed in a concave state on the outer circumferential face, and a magnetic head having a size smaller than the window portion and disposed in the window portion such that a pair of air gaps having an equal width are formed between the opposite leading and trailing ends of the magnetic head on the one hand and the opposite leading and trailing ends of the window portion on the other hand, respectively, the magnetic head advancing in a predetermined advancing direction by rotation of the outer circumferential face of the rotary drum, the magnetic head having a smooth flat face which extends perpendicularly to a diametrical direction of the rotary drum and is positioned on the inner circumferential side retracted from the outer circumferential face of the rotary drum such that the smooth flat face moves by rotation of the rotary drum and is opposed to the tape-type magnetic recording medium to fluidically interfere with the tape-type magnetic recording medium and a recording and/or playback element disposed on the trailing side with respect to the center on the smooth flat face in the advancing direction for contacting and magnetically interfering with the tape-type magnetic recording medium to execute at least one of recording and playback of the tape-type magnetic recording medium.
In the rotary magnetic head mechanism, the face portion having a size smaller than a window portion formed in a concave state on the outer circumferential face of the rotary drum for fluidically interfering with a tape-type magnetic recording medium is disposed as a smooth flat face which extends perpendicularly to a diametrical direction of the rotary drum and is positioned on the inner circumferential side retracted from the outer circumferential face of the rotary drum so as to form a pair of air gaps between the opposite ends of the window portion and the opposite ends of the face portion, and the recording and/or playback element for magnetically interfering with the tape-type magnetic recording medium is disposed on the trailing side with respect to the center on the smooth flat face. When the drum rotates, the pressures within the air gaps having an equal width and formed between the opposite ends of the magnetic head and the opposite ends of the window portion are reduced, and consequently, the tape-type magnetic recording medium is attracted toward the smooth flat face of the rotary drum positioned on the inner circumferential side retracted from the outer circumferential face of the rotary drum. However, the peak of an attraction locus is displaced to the trailing side with respect to the center by the inertia of the tape-type magnetic recording medium.
Meanwhile, since the smooth flat face of the magnetic head extends perpendicularly to a diametrical direction of the rotary drum, when the rotary drum rotates, the smooth flat face advances in a tangential direction to the rotary drum, whereupon an air flow is formed in the tangential direction on the smooth flat face. The air flow flows along a narrow path defined by the smooth flat face and the tape-type magnetic recording medium having approached the smooth flat face by the attraction described above. As a result, pressure reduction in accordance with the Bernoulli""s theorem occurs with the air flow. Due to the pressure reduction effect, the tape-type magnetic recording medium gradually approaches the smooth flat face, and in accordance with the displacement of the peak described above, the tape-type magnetic recording medium contacts principally with a portion of the smooth flat face on the trailing side with respect to the center. Consequently, the tape-type magnetic recording medium contacts with a contact pressure with the recording and/or playback element disposed on the trailing side in the advancing direction with respect to the center on the smooth flat face. In this manner, the tape-type magnetic recording medium can be contacted with the recording and/or playback element with a suitable contact pressure only by the pressure reduction effect of the air flow generated naturally without the necessity for applying compulsory force. Consequently, recording or playback can be performed while suppressing abrasion of the tape-type magnetic recording medium and the magnetic head.
Preferably, the smooth flat face is disposed in a displaced relationship to the outer circumference side until the tape-type magnetic recording medium having been contacted with and then spaced away from the smooth flat face passes by the trailing end of the window portion without colliding or contacting with the trailing end of the window portion.
In the rotary magnetic head mechanism, since the smooth flat face is disposed in a displaced relationship to the outer circumference side, the tape-type magnetic recording medium having been contacted with and then spaced away from the smooth flat face passes by the trailing end of the window portion without colliding or contacting with the trailing end of the window portion. Consequently, otherwise possible damage to the tape-type magnetic recording medium can be prevented.
According to a yet further aspect of the present invention, there is provided a rotary magnetic head mechanism, comprising a cylindrical rotary drum having an outer circumferential face along which a tape-type magnetic recording medium can be wrapped and which rotates at a predetermined linear velocity in a tangential direction and a window portion formed in a concave state on the outer circumferential face, and a magnetic head having a size smaller than the window portion and disposed in the window portion such that an air gap formed between a leading end of the magnetic head and a leading end of the window portion has a width smaller than that of another air gap formed between a trailing end of the magnetic head and a trailing end of the window portion, the magnetic head advancing in a predetermined advancing direction by rotation of the outer circumferential face of the rotary drum, the magnetic head having a smooth flat face which extends perpendicularly to a diametrical direction of the rotary drum and is positioned on the inner circumferential side retracted from the outer circumferential face of the rotary drum such that the smooth flat face moves by rotation of the rotary drum and is opposed to the tape-type magnetic recording medium to fluidically interfere with the tape-type magnetic recording medium and a recording and/or playback element disposed within a range on the face portion within which the tape-type magnetic recording medium contacts with the face portion with fluidic interference for contacting and magnetically interfering with the tape-type magnetic recording medium to execute at least one of recording and playback of the tape-type magnetic recording medium.
In the rotary magnetic head mechanism, the face portion having a size smaller than a window portion formed in a concave state on the outer circumferential face of the rotary drum for fluidically interfering with a tape-type magnetic recording medium is disposed as a smooth flat face which extends perpendicularly to a diametrical direction of the rotary drum and is positioned on the inner circumferential side retracted from the outer circumferential face of the rotary drum such that an air gap formed between a leading end of the magnetic head and a leading end of the window portion has a width smaller than that of another air gap formed between a trailing end of the magnetic head and a trailing end if the window portion, and the recording and/or playback element for magnetically interfering with the tape-type magnetic recording medium is disposed within a contact range between the smooth flat face and the tape-type magnetic recording medium. Not only because the smooth flat face which acts to attract the tape-type magnetic recording medium is positioned on the leading side in the direction of rotation in the window portion, but also because, when the drum rotates, the pressure reduction in the air gap of a smaller width on the leading side is greater than the pressure reduction in the air gap of a greater width on the trailing side, the peak of an attraction locus of the tape-type magnetic recording medium attracted toward the smooth flat face positioned on the inner circumferential side retracted from the outer circumferential face of the rotary drum is not displaced to the trailing side with respect to the center by the inertia of the tape-type magnetic recording medium but is formed on the leading side.
Meanwhile, since the smooth flat face of the magnetic head extends perpendicularly to a diametrical direction of the rotary drum, when the rotary drum rotates, the smooth flat face advances in a tangential direction to the rotary drum, whereupon an air flow is formed in the tangential direction on the smooth flat face. The air flow flows along a narrow path defined by the smooth flat face and the tape-type magnetic recording medium having approached the smooth flat face by the attraction described above. As a result, pressure reduction in accordance with the Bernoulli""s theorem occurs with the air flow. Due to the pressure reduction effect, the tape-type magnetic recording medium gradually approaches the smooth flat face, and in accordance with the displacement of the peak to the leading side described above, the tape-type magnetic recording medium contacts principally with a portion of the smooth flat face on the leading side with respect to the center. Consequently, the tape-type magnetic recording medium contacts with a contact pressure with the recording and/or playback element disposed on the smooth flat face. In this manner, the tape-type magnetic recording medium can be contacted with the recording and/or playback element with a suitable contact pressure only by the pressure reduction effect of the air flow generated naturally without the necessity for applying compulsory force. Consequently, recording or playback can be performed while suppressing abrasion of the tape-type magnetic recording medium and the magnetic head.
Further, since the position at which the tape-type magnetic recording medium is spaced away from the smooth flat face after the contact with the latter is displaced on the leading side by the displacement of the peak to the leading side described above and besides the tape-type magnetic recording medium when passes by the air gap of a greater width on the trailing side is attracted by comparatively low attracting force because the pressure reduction in the air gap of a greater width on the trailing side is small, the tape-type magnetic recording medium can pass by the trailing end of the window without colliding or contacting with the latter. Consequently, otherwise possible damage to the tape-type magnetic recording medium can be prevented.
In any of the rotary magnetic head mechanisms described above, the face portion opposing to the tape-type magnetic recording medium may be formed from a smooth curved face having a curvature more moderate than that of the rotary drum and having a tangential direction at least at one position thereof which extends perpendicularly to a diametrical direction of the rotary drum. In the rotary magnetic head mechanism, since a tangential direction at least at one position of the smooth curved face extends perpendicularly to a diametrical direction of the rotary drum, an air flow is formed in the same direction as the advancing direction of the magnetic head on the smooth curved face. The air flow flows along a narrow path defined by the tape-type magnetic recording medium and the smooth curved face of a moderate curvature of the magnetic head. As a result, pressure reduction in accordance with the Bernoulli""s theorem occurs with the air flow, and by the pressure reduction effect, contact of the tape-type magnetic recording medium with the recording and/or playback element can be assured.
In summary, the following advantages can be achieved by the present invention.
1. Since a synergetic effect is achieved by the first stage wherein the magnetic tape is attracted toward the head by an effect by the channel configuration or by an effect by the configuration wherein the head is positioned at a retracted position and the second stage wherein the pressure reduction effect by an air stream generated naturally on the face of the head when the head rotates is utilized subsequently to contact the attracted magnetic head with the head, a sufficiently low contact pressure to the head which does not have any problem for magnetic recording or playback can be obtained stably.
2. Various problems arising from abrasion of the head can be solved, and a long life can be assured for the head.
3. Increase of the life of the magnetic tape can be achieved simultaneously.
4. Since the abrasion of the head is very small, the gap depth can be reduced as much, and consequently, recording/playback of a high sensitivity and a high density can be anticipated.
5. The head can be formed in a reduced size.
6. A head of the contact type wherein the magnetic tape and the head contact with each other such as, for example, an MR head or a GMR head of the magneto-resistance effect type (or magnetic flux response type) wherein a magnetic field variation on a recording medium can be detected with a very small gap depth making use of a magneto-resistance effect can be applied for recording or playback of a tape-type magnetic recording medium.
The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings in which like parts or elements denoted by like reference symbols.